Update checkout action to v6 (#423)

Author: mcbarton

.github/workflows/clang-format.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-22.04
     steps:
       - name: Checkout PR branch
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           ref: ${{ github.event.pull_request.head.sha }}
           fetch-depth: 0

.github/workflows/clang-tidy-review.yml

@@ -17,7 +17,7 @@ jobs:
 
     steps:
       - name: Checkout PR branch
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Setup Python
         uses: actions/setup-python@v6

.github/workflows/deploy-github-page.yml

@@ -26,7 +26,7 @@ jobs:
             os: ubuntu-24.04
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
 

.github/workflows/main.yml

@@ -61,7 +61,7 @@ jobs:
             micromamba_shell_init: cmd.exe
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
 
@@ -206,7 +206,7 @@ jobs:
             os: macos-15
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0